One method for producing liquid from a hydrocarbon well employs an electrical submersible pump (ESP) located within the well. The ESP includes an electrical motor that drives the pump. The motor has a stator with windings that are supplied with three-phase power, inducing an electromagnetic field that causes a rotor and drive shaft to spin. A dielectric lubricant fills the motor. A seal section or pressure equalizer mounts to the motor and has a pressure compensating member that equalizes the pressure of the lubricant with the hydrostatic pressure of well fluid in the well.
Operating the motor causes heat to be generated in the windings. Also, the temperature of the well fluid in some wells can be quite high. The temperatures of the windings have a direct impact on the degradation rate of insulating materials in the motor. Preventing the motor from excessive heating is an important goal.
Various proposals have been made to mitigate degradation of the insulating materials. Those proposals include mounting a lubricant pump in the motor and circulating the dielectric fluid. Fins on the exterior of the motor have been proposed to increase heat transfer from the motor to the surrounding well fluid. Another technique involves lubricant circulation tubes on the exterior of the motor. For subsea applications, one proposed technique is to employ an external heat exchanger that is submersed in the sea. The dielectric lubricant circulates through the heat exchanger. High temperature insulation materials may be used.